1. Field of the Invention
The present invention relates to an electronic toothbrush and, more specifically, to a combination of an electronic toothbrush for effectively removing bacterial plaque on the teeth by causing electric current to flow between the teeth and the toothbrush, and a tester for detecting the voltage of the electric power source of the toothbrush.
2. Description of the Related Art
Many proposals have hitherto been made on electronic toothbrushes adapted to cause electric current to flow between the teeth and the toothbrush so as to effectively remove bacterial plaque on the teeth and enhance the permeation of fluorides contained in the dentifrice (e.g., Japanese Patent Publication No. 27390/1973, and Japanese Utility Model Publication No. 5092/1968). However, such conventional electronic toothbrushes have failed to successfully come into general use because their complicated structures involve high production costs, and also because they can be handled only with difficulty. In order to overcome these drawbacks, the present applicant has previously proposed an electronic toothbrush, described in Japanese Patent Publication No. 1842/1988.
In order that an electronic toothbrush can properly perform its function, the power source voltage must be maintained at a predetermined value. Therefore, if the electronic toothbrush has a structure in which an electric power source, such as a battery, is disposed in the grip portion of the toothbrush, the voltage of the power source must be checked periodically. For this purpose, the present applicant has previously proposed a voltage tester, described in Japanese Patent Laid-open Publication No. 64968/1987, so that the user will be urged to check the voltage of the built-in power source of an electronic toothbrush periodically by means of the voltage tester.
The voltage tester previously proposed by the present applicant is advantageous in that it can be operated with ease. Thus, this voltage tester is designed to make the operation of checking the voltage of the power source of an electronic toothbrush as simple as possible so that the user will not fail to attend to the operation. However, because the voltage tester is a body separate from the electronic toothbrush, and is an instrument that need not be used at every tooth-brushing, it is necessary for the voltage tester to be stored in a certain place when not in use, and be taken out when necessary. This means that the voltage checking operation can still be troublesome in view of the fact that the users may sometimes even fail to attend to their daily tooth-brushing.
The present applicant has previously made proposals, for example, in Japanese Patent Application No. 133053/1989 (filed on May 26, 1989), on structures where a voltage-detecting function is incorporated in an electronic toothbrush. However, such a structure is rather complicated and involves an increase in the production cost.